1. Field of the Invention
The present invention relates to an optical switcher used in a signal transmission/distribution system or the like used in a broadcast station.
2. Description of the Related Art
In the past, optical switchers having a plurality of inputs and outputs have been developed for cross connection in a trunk transmission network. In general, cross connection in the trunk transmission network is only required to implement a N-to-N nonblocking switching, and is not required to implement a one-to-N broadcasting mode connection. To the contrary, switchers used in a broadcast station or the like are required to have a capability of signal distribution, and thus, the one-to-N broadcasting mode connection is required. Conventionally, only switching of an uncompressed SDTV (Standard Definition Television) serial digital signal transferred at a rate of 270 Mb/s at most was needed, and thus, the one-to-N broadcasting mode connection could be readily realized electrically by electrical switchers.
Recently, broadcast stations have been required to transmit and switch an uncompressed HDTV (High Definition Television) serial digital signal at a transfer rate of 1.5 Gb/s. In order to transmit the serial digital signal at a rate of 1.5 Gb/s for 100 meters or more, optical fiber transmission is essentially used. At present, as shown in FIG. 1, optical fiber transmission and an electrical switcher are used. In FIG. 1, reference numeral 101 denotes an electric-optic (E/O) converter for converting an input serial digital signal into an optical signal, reference numeral 102 denotes an optical fiber for transmitting the optical signal sent from the E/O converter 101, reference numeral 103 denotes an opto-electric (O/E) converter for converting the optical signal received from the optical fiber 102 into an electric signal (serial digital signal), reference numeral 104 denotes an electrical switcher for switching the serial digital signal, reference numeral 105 denotes an E/O converter for converting the serial digital signal output from the electrical switcher 104 into an optical signal, reference numeral 106 denotes an optical fiber for transmitting the optical signal sent from the E/O converter 105, and reference numeral 107 denotes an O/E converter for converting the optical signal received from the optical fiber 106 into an electric signal (serial digital signal).
In such a conventional signal transmission/distribution system, the O/E converters 103, the O/E converter 105 and the electrical switcher 104 are necessarily located on the optical fiber transmission path. Therefore, the system becomes disadvantageously complicated. If an optical switcher enabling one-to-N broadcasting mode connection is provided, transmission and switching can be accomplished optically, and thus, the system can be simplified and the cost can be reduced.